There are numerous types of pulling devices for pulling bolts and broaching holes, and broacher type equipment has been used for pulling mandrels to cold work holes. These pullers are heavy, require an air line for controlling a pneudraulic unit and another air line for returning the mandrel to starting position. When the hydraulic unit reaches the bottom of a stroke the hydraulic pressure builds up to maximum pressure capacity of the hydraulic pump; which requires a very heavy puller unit. The units do not automatically shut off at the end of a pulling stroke, therefore an operator tries to anticipate, and as a result turns the power off and on during a pulling cycle.
The power required for a pulling cycle can be very high. As high pressure is applied to a hydraulic cylinder the cylinder wall increases in diameter due to the elasticity of the material. The piston on the other hand does not expand radially at anything like the rate the cylinder expands. Therefore, the clearance between the piston and the cylinder increases with an increase in pressure and allows an O-ring seal to extrude in the gap, and result in a short seal life. The thickness of the cylinder wall may be increased to prevent this difficulty, but this adds to the weight of the hand-tool.